1. Field of the Invention
This invention relates to a camera arranged to perform operation control by means of a computer.
2. Description of the Related Art
Heretofore, the CPU (central processing unit) adapted for use in a camera has been arranged for the purpose of controlling load circuits. Under a normal low-load, non-driving condition, the CPU is kept in a hold state in which current consumption remains at a low level for preventing a power source battery from being wasted. The hold state is cancelled and shifted to an operative state in starting control over various circuits by allowing an oscillation circuit to operate only when some load must be driven, for example, in response to an operation on the shutter release button of the camera. The hold state has been arranged to be cancelled by supplying an ON signal representing a closed state of a switch SW1 which is interlocked with the release button to the hold control terminal of the CPU either directly or via a chattering absorption circuit and a logic circuit. However, the above stated conventional arrangement has presented problems as described below:
(i) With the ON signal of the switch SW1 arranged to be directly supplied, the hold state is often cancelled by external noise, static electricity, etc. The power source battery tends to be consumed by this. Further, in some case, this causes a whole photo-taking operation to be ruined by a faulty action of the CPU.
(ii) The above-stated problem (i) may be effectively solved by adding a chattering absorption circuit to the camera. However, the addition of this circuit solely for this purpose is expensive and also disadvantageous in terms of space.
(iii) It is always possible that the photographer might untimely free the shutter release button from a depressing operation thereon before completion of a photo-taking process. To prevent this, therefore, the camera must be provided with some holding means, which, however, makes the camera designing work very troublesome.
Further, the loads on the camera often include not only a first group of load circuits which must be operated under the control of the CPU by rendering the CPU operative, such as control over an AF circuit, etc. but also a second group of many load circuits which can be allowed to operate without any control by the CPU such as an electric charging operation on a flash circuit, etc. The camera of this kind does not have to have the CPU always rendered operative in driving loads. If the CPU is arranged to be rendered operative in driving any of the second group of load circuits, the power source battery would be wastefully consumed.
Since the actions of the first group of load circuits must be controlled by the CPU while they are driven, the CPU must unfailingly be kept operative while any of the loads is driven. However, it is preferable that, after completion of the load driving operation, the CPU is immediately brought into a hold state. In the case of the second group of load circuits, the CPU must be shifted to the hold state immediately after commencement of a driving operation on the loads.